1. Field of the Invention
The present invention relates to a vacuum process apparatus of the kind, including at least two stations for treating or handling the workpiece, and a transport device with conveyor means thereon, each for transporting at least one workpiece from station to station.
2. Description of the Prior Art
The German specification DE-A-24 54 544 and "Patent Abstracts of Japan", Nov. 28, 1989, vol. 13, no. 532, JP-A2 1-218 627, disclose as an example such a vacuum process apparatus which includes at least two stations, each comprising an opening for an article, the openings each determining an opening area with surface normal A.sub.n perpendicular to the opening area F such as illustrated in FIG. 1 for sake of clarity. The said apparatus further includes a transport device which is supported and driven to rotate around a space axis as rotational axis and includes at least one conveyor portion for an article, whereby the conveyor portion is moved consecutively to and from the openings of the stations.
In contrary to the design of the apparatus according to the JP-1-218627, the transport device of which comprising only one conveyor portion for an article and whereat the conveyor portion is rigidly fixed on a rotatable cylinder forming the transport device, the apparatus according to the German patent no. 24 54 544 comprises four conveyor portions for articles. These conveyor portions are additionally movable with respect to the transport device. By means of a driving plunger there is realized for each conveyor portion an individual drive for moving the said conveyor portion of the transport device relative to a respective station.
Thus, according to the apparatus of the German patent no. 24 54 544, the conveyor portion may be positioned at different positions with respect to a respective station, according to the specific requirements of a process performed at the station considered, up to providing for a sealing closure of the said opening by means of the conveyor portion.
Provision of the said driving plungers which are led through the wall of the vacuum recipient has different drawbacks:
a) For every driving plunger there must be provided a dynamic gliding vacuum seal which results in a considerable additional expenditure for the apparatus in view of vacuum technical requirements for such dynamic seals.
b) The said driving plungers are individually associated to respective stations. Thus, if an apparatus or vacuum plant shall be changed by changing the number of process stations mounted thereon and especially shall be changed by raising the number of such process stations provided, the complete apparatus with its vacuum recipient must be changed according to the changing number of vacuum tight mounted driving plungers.
It is a first object of the present invention to remedy these drawbacks and to provide a vacuum process apparatus which comprises a self-comprised transport device which may flexibly be used for a great number of different apparatus configurations with respect to the number of the process stations provided.
The design of vacuum process apparatuses according to the DE-A-24 54 544 which have established themselves on the market has the further drawback that the rotational axis around which the transport device is rotatable extends parallel to the normals of the opening areas. Thereby the openings of the stations are distributed equidistantly around the rotational axis i.e. the rotational axis of the transport device, so that, as an advantage, the openings of the stations can be served solely by a pivoting movement of the transport device around the rotational axis. Nevertheless, it is disadvantageous that when designing the vacuum process apparatus, there is a restriction in constructional freedom, in that the individual stations must be located with the said normals of their opening areas extending parallel to the rotational axis of the transport device. This necessitates that the stations must be arranged in one given orientation with respect to the transport device, possibly may be provided at both sides of the plane swept over by the transport device of said DE-A-24 54 544.
It is thus a further object of the present invention to remedy this drawback and to provide a vacuum process apparatus with a transport device-to station openings-relation which allow a significantly improved constructional freedom for such apparatus.